The present invention relates to an apparatus for replaceably connecting a casting tube to a closable pouring spout of a tundish of a continuous casting plant, particularly for the continuous casting of metal bars of small cross sections, wherein the casting tube extends into a permanent ingot mold to maintain molten metal being discharged from the pouring spout out of contact with the surrounding air. More particularly, the present invention relates to such an apparatus of the type including a gimbal device for supporting the casting tube and a double-arm lever including a first arm supporting the gimbal device and the casting tube and a second arm carrying a counterweight, the lever being pivoted about an axis such that the first arm and the gimbal device press the casting tube against the mouth of the pouring spout.
It is common practice to employ a casting tube on the spout of a tundish to protect the molten metal being discharged from the tundish from being oxidized on its way to a mold and to enable the molten metal to be poured quietly and distributed uniformly across the cross section of the mold. During such process, the casting tube, formed of a refractory material, is subjected to enormous thermal, erosive and chemical attacks. Such casting tubes therefore wear rapidly and must be replaced often during the life of the other elements of the casting operation, and particularly must be replaced within the casting times possible for sequence casting, particularly during continuous casting. The replacement of a casting tube that has become useless through wear must be effected rapidly and reliably to maintain the continuous casting formation in the mold.
Counterweight devices of this general type that function according to the principle of a counter fastening of the casting tube to the spout by means of a two-arm lever, unlike cotter or bayonet-type fittings, enable a simple mounting and removal of the casting tube, and thereby provide for a rapid exchange or replacement of the casting tube, generally known as a "flying exchange", when interrupting the casting operation in a continuous casting sequence. Presently, such known devices mainly are employed in continuous casting plants using permanent ingot molds with a relatively small cross section. In such operations, chilling of the molten metal, for example steel, and thereby slag formation on the casting tube that dips into the molten steel, cannot be ruled out. When such occurs, a removal force can be transmitted from the cast bar through the casting tube to the counterweight, with the result that the casting tube will be released from the spout against the force of the counterweight. A gap results, through which the molten metal is forced outwardly before a stopper of the tundish is closed. This creates the danger of an accident and can lead to considerable damage.